1. Field of the Invention
The present invention relates to a perpendicular magnetic recording head for writing by applying a perpendicular magnetic field to a recording medium, such as a disk having a hard film, and to a method for making the same. More particularly, the invention relates to a perpendicular magnetic recording head which suppresses fringing in a recorded pattern and which is suitable for an increased recording density, and to a method for making the same.
2. Description of the Related Art
In a perpendicular magnetic recording apparatus, magnetic data is written in a recording medium, such as a disk, at high densities. FIG. 27 is a sectional view which shows a general structure of a perpendicular magnetic recording head used in a perpendicular magnetic recording apparatus.
As shown in FIG. 27, a perpendicular magnetic recording head H is provided on a trailing edge of a slider 1 which floats above or slides over a recording medium. For example, the perpendicular magnetic recording head H is disposed between a nonmagnetic film 2 and a nonmagnetic coating film 3 on a trailing edge 1a of the slider 1.
The perpendicular magnetic recording head H includes an auxiliary magnetic pole layer 4 composed of a ferromagnetic material and a main magnetic pole layer 5 composed of a ferromagnetic material formed at a distance from the auxiliary magnetic pole layer 4. A front end 4a of the auxiliary magnetic pole layer 4 and a front end 5a of the main magnetic pole layer 5 are exposed at a surface Ha facing a recording medium Md. The auxiliary magnetic pole layer 4 and the main magnetic pole layer 5 are magnetically coupled to each other at a magnetic coupling section which is provided toward the back from the surface Ha.
A nonmagnetic insulating layer 7 composed of an inorganic material, such as Al2O3 or SiO2, is placed between the auxiliary magnetic pole layer 4 and the main magnetic pole layer 5. A front end 7a of the nonmagnetic insulating layer 7 is exposed at the surface Ha between the front end 4a and the front end 5a. 
A coil layer 8 composed of a conductive material, such as Cu, is embedded in the nonmagnetic insulating layer 7.
As shown in FIG. 27, a thickness hw of the front end 5a of the main magnetic pole layer 5 is smaller than a thickness hr of the front end 4a of the auxiliary magnetic pole layer 4. The width in the track width direction (in the X direction in the drawing) of the front end 5a of the main magnetic pole layer 5 corresponds to a track width Tw, which is sufficiently smaller than the width in the track width direction of the front end 4a of the auxiliary magnetic pole layer 4.
The recording medium Md on which magnetic recording is performed by the perpendicular magnetic recording head H moves in the Y direction relative to the perpendicular magnetic recording head H. The recording medium Md is provided with a hard film Ma on the surface and with a soft film Mb inside.
When a recording magnetic field is induced to the auxiliary magnetic pole layer 4 and the main magnetic pole layer 5 by applying an electrical current to the coil layer 8, a leakage recording magnetic field between the front end 4a of the auxiliary magnetic pole layer 4 and the front end 5a of the main magnetic pole layer 5 is transmitted through the hard film Ma perpendicularly and then passes through the soft film Mb. Since the area of the front end 5a of the main magnetic pole layer 5 is sufficiently smaller than the area of the front end 4a of the auxiliary magnetic pole layer 4, magnetic flux "PHgr" is concentrated in the front end 5a of the main magnetic pole layer 5, and magnetic data is written in the hard film Ma at the section facing the front end 5a by the magnetic flux "PHgr".
FIG. 28 is a partial front view of the perpendicular magnetic recording head shown in FIG. 27, viewed from the surface Ha. The main magnetic pole layer 5 is formed on a plating underlayer 5b composed of a magnetic material by plating using a magnetic material. The main magnetic pole layer 5 has a curved upper surface 5c in a convex form. In the conventional perpendicular magnetic recording head, sides 5d of the main magnetic pole layer 5 are perpendicular to the track width direction (the X direction in the drawing).
FIG. 29 is a plan view of a recording track on a recording medium in which signals have been written by the perpendicular magnetic recording head shown in FIGS. 27 and 28.
When the slider 1 moves between the outside periphery and the inside periphery, a skew angle may occur in which the sides 5d of the main magnetic pole layer 5 are inclined relative to a tangent of moving of the recording medium Md (the Y direction). If the sides 5d of the main magnetic pole layer 5 are perpendicular to the track width direction, when the sides 5d have a skew angle relative to the tangent of moving of the recording medium Md (the Y direction), the sides 5d of the main magnetic pole layer 5 apply an oblique leakage magnetic field to the outside of the track width Tw1 as illustrated by broken lines in FIG. 29, and fringing F is generated, resulting in a degradation in offtrack performance.
If the upper surface 5c of the main magnetic pole layer 5 is a curved surface in a convex form, domain boundaries B1 are curved and the pulse width of a regenerated waveform is increased. As a result, if the recording density is increased, it is not possible to obtain a clear distribution of recording magnetization. Therefore, it becomes difficult to increase the recording density in the longitudinal direction of the recording track (in the A direction).
Objects of the present invention are to provide a perpendicular magnetic recording head which can suppress fringing in a recorded pattern, which can improve the offtrack performance, and which can improve the recording density in the longitudinal direction of a recording track, and to provide a method for making the same.
In one aspect of the present invention, a perpendicular magnetic recording head includes an auxiliary magnetic pole layer exposed at a surface facing a recording medium; a main magnetic pole layer exposed at the surface facing the recording medium, the main magnetic pole layer being deposited on the auxiliary magnetic pole layer with an insulating layer therebetween; a coil layer for applying a recording magnetic field to the auxiliary magnetic pole layer and the main magnetic pole layer, the coil layer being provided toward the back from the surface facing the recording medium, wherein magnetic data is written in the recording medium by the magnetic field concentrating in the main magnetic pole layer perpendicular to the plane of the recording medium; and a connecting layer placed on the auxiliary magnetic pole layer toward the back from the surface facing the recording medium, the main magnetic pole layer and the connecting layer being magnetically coupled to each other directly or by a yoke layer formed on the main magnetic pole layer and on the connecting layer. At the surface facing the recording medium, the upper base of the main magnetic pole layer is wider than the lower base at the auxiliary magnetic pole layer side of the main magnetic pole layer so that the width in the track width direction of the main magnetic pole layer gradually increases with distance from the auxiliary magnetic pole layer.
In the present invention, at the surface facing the recording medium, the upper base of the main magnetic pole layer is wider than the lower base of the main magnetic pole layer so that the width in the track width direction of the main magnetic pole layer gradually increases with distance from the auxiliary magnetic pole layer. That is, at the surface facing the recording medium, the main magnetic pole layer has a substantially inverted trapezoidal front end.
Consequently, when writing is performed on the recording medium, even if the sides of the main magnetic pole layer have a skew angle relative to the tangent of moving of the recording medium, it is possible to prevent the sides from protruding from the recording track, and thus fringing can be avoided, resulting in an improvement in offtrack performance.
Preferably, in the present invention, at the surface facing the recording medium, the upper base of the main magnetic pole layer is linear.
The recording medium travels from the auxiliary magnetic pole layer side of the perpendicular magnetic recording head to the yoke layer side. Therefore, the shape of the magnetic boundaries of the recording track on the recording medium depends on the shape of the upper base of the main magnetic pole layer.
If the upper base of the main magnetic pole layer is linear, the magnetic boundaries of the recording track are also linear, and even if the recording density in the longitudinal direction of the recording track is increased, it is possible to obtain a clear distribution of recording magnetization, and thus satisfactory read/write characteristics can be obtained.
Preferably, in the present invention, the main magnetic pole layer is formed by plating on a plating underlayer composed of a nonmagnetic metallic material.
When the plating underlayer is composed of the nonmagnetic metallic material, the width in the track width direction of the plating underlayer may be larger than the width in the track width direction of the bottom of the main magnetic pole layer.
Preferably, in the present invention, the main magnetic pole layer is formed on a plating underlayer composed of a magnetic material, at least a part of the sides in the track width direction of the plating underlayer protrudes from either end in the track width direction of the lower base at the auxiliary magnetic pole layer side of the main magnetic pole layer, and the protrusion does not exceed a recording track width Tw1 written in the recording medium when a skew angle occurs during writing.
When the main magnetic pole layer is formed on the plating underlayer composed of the magnetic material, preferably, the width in the track width direction of the plating underlayer is smaller than the width in the track width direction of the lower base of the main magnetic pole layer.
If the width in the track width direction of the plating underlayer is in the range described above, when writing is performed on the recording medium, even if the sides of the main magnetic pole layer have a skew angle relative to the tangent of moving of the recording medium, it is possible to prevent the plating underlayer from protruding from the recording track, and thus fringing can be avoided.
Preferably, in the present invention, the area of a front end of the main magnetic pole layer exposed at the surface facing the recording medium is sufficiently smaller than the area of a front end of the auxiliary magnetic pole layer exposed at the surface facing the recording medium, and at a cross section parallel to the surface facing the recording medium, the cross-sectional area of the main magnetic pole layer is smaller than the cross-sectional area of the yoke layer.
Preferably, in the present invention, the saturation magnetic flux density of the main magnetic pole layer is higher than the saturation magnetic flux density of the yoke layer.
Preferably, a front end of the yoke layer is placed toward the back from the surface facing the recording medium.
In another aspect of the present invention, a method for making a perpendicular magnetic recording head includes:
a step (a) of forming an auxiliary magnetic pole layer using a magnetic material;
a step (b) of forming a connecting layer on the auxiliary magnetic pole layer using a magnetic material toward the back from a surface facing a recording medium;
a step (c) of forming a coil layer in a region toward the back from the surface facing the recording medium;
a step (d) of depositing an insulating layer on the auxiliary magnetic pole layer and forming a plating underlayer on the insulating layer;
a step (e) of forming a resist layer on the plating underlayer and forming a recess in the resist layer at a section for forming the surface facing the recording medium, the inner width in the track width direction of the recess gradually increasing with distance from the auxiliary magnetic pole layer, the recess having a predetermined depth toward the back from the surface facing the recording medium;
a step (f) of forming a main magnetic pole layer by plating in the recess and then removing the resist layer; and
a step (g) of magnetically coupling the main magnetic pole layer and the connecting layer to each other directly or by forming a yoke layer on the main magnetic pole layer and on the connecting layer.
In the method for making the perpendicular magnetic recording head of the present invention, in step (e), a recess is formed in the resist layer so that the inner width in the track width direction of the recess gradually increases with distance from the auxiliary magnetic pole layer and the recess has a predetermined depth toward the back from the surface facing the recording medium. In step (f), a main magnetic pole layer is formed by plating in the recess.
That is, in the main magnetic pole layer of the perpendicular magnetic recording head thus obtained, at the surface facing the recording medium, the upper base of the main magnetic pole layer is wider than the lower base at the auxiliary magnetic pole layer side of the main magnetic pole layer so that the width in the track width direction gradually increases with distance from the auxiliary magnetic pole layer. That is, the main magnetic pole layer has a substantially inverted trapezoidal front end.
In step (e), in order to form the recess so that the inner width in the track width direction gradually increases with distance from the auxiliary magnetic pole layer, in step (e), preferably, the resist layer is formed on the plating underlayer and the recess is formed by patterning in the resist layer, and then the resist layer is heat-treated.
Alternatively, in step (e), preferably, the resist layer is formed on the plating underlayer and the recess is formed by patterning in the resist layer by adjusting the patterning accuracy of the resist layer so that the inner width in the track width direction gradually increases with distance from the auxiliary magnetic pole layer.
In the present invention, the method may further include, between step (f) and step (g), a step (h) of planarizing the upper surface of the main magnetic pole layer by milling, wherein milling particles are emitted at a predetermined angle with respect to the center line of the main magnetic pole layer. By planarizing the upper surface of the main magnetic pole layer, at the surface facing the recording medium, the upper base of the main magnetic pole layer is set to be linear.
The method may further include, between step (f) and step (g), a step (i) of etching the sides of the main magnetic pole layer by milling to set the width in the track width direction of the main magnetic pole layer, wherein milling particles are emitted at a predetermined angle with respect to the center line of the main magnetic pole layer.
The method may further include, between step (f) and step (g), a step (j) of removing the plating underlayer in a region other than the region underlying the main magnetic pole layer by milling, wherein milling particles are emitted at a predetermined angle with respect to the center line of the main magnetic pole layer, and then removing the material of the plating underlayer adhering to the sides of the main magnetic pole layer by the milling.
In the present invention, the method may further include, between step (f) and step (g), a step (k) of planarizing the upper surface of the main magnetic pole layer by milling, wherein milling particles are emitted at a predetermined angle with respect to the center line of the main magnetic pole layer, and then performing the removal of the plating underlayer in a region other than the region underlying the main magnetic pole layer, the removal of the material of the plating underlayer adhering to the sides of the main magnetic pole layer, and etching of the sides of the main magnetic pole layer to set the width in the track width direction of the main magnetic pole layer simultaneously by the milling.
Preferably, in step (h), (i), (j), or (k), the predetermined angle is 45xc2x0 to 80xc2x0. More preferably, the predetermined angle is 60xc2x0 to 70xc2x0.
In step (d), the plating underlayer may be formed using a magnetic material or a nonmagnetic material.
If the plating underlayer is composed of a nonmagnetic material, even if the unwanted plating underlayer remains in a region other than the region underlying the main magnetic pole layer when the unwanted plating underlayer is removed after the formation of the main magnetic pole layer, the recording characteristics of the perpendicular magnetic recording head are not greatly affected.
Consequently, if the plating underlayer is composed of the nonmagnetic material, when the plating underlayer is removed in the region other than the region underlying the main magnetic pole layer in step (j) or (k), the width in the track width direction of the plating underlayer may be set larger than the width in the track width direction of the bottom of the main magnetic pole layer.